Normal goods are those which have income effect positive i.e. when income of the consumer increases, the demand for the commodity increases and vice-versa.
Inferior goods are those which have income effect negative i.e as income of the consumer increases, the demand for the commodity falls and vice-versa.
For example, toned milk and full cream milk. For a consumer toned milk is an inferior good and full cream milk is a normal good. An increase in income of the consumer will induce the consumer to shift to full cream milk from toned milk. Similarly a fall in income will induce the consumer to consume less of full cream milk and shift to toned milk.